It took about 450 million years, but the Utica Shale is finally having its moment in the sun.

Seven deals involving the Ohio oil and gas formation totaled $6.7 billion in 2011 — a huge increase from the single transaction worth $178 million in 2010.

The liquids-rich formation that overlaps and borders the Marcellus Shale benefited from increased interest in oil-rich regions, which become more lucrative when natural gas prices fall as they have in the past year.

Still, oil and gas activity in the United States in 2011 jumped nearly $50 billion, with 191 deals accounting for $186.5 billion spent, according to the latest report from the analysis arm of New York-based PricewaterhouseCoopers LLC. The analysis studied American energy mergers and transactions worth more than $50 million.

Those deals can include huge acreage sales between companies or investments from third parties, such as other countries or private equity firms.

In 2011, the number of deals fell but the average value of each rose. The average deal size in 2011 was $977 million, up 38 percent from the previous year.

There was a similar trend among foreign investors in American oil and gas. In 2011, foreign buyers completed 40 transactions worth $56.4 billion. That’s five fewer than in 2010, but a 55 percent increase in deal value.